What's the difference between 78K0/Kx2 and 78K0S/Kx1+?

Question:

What's the difference between 78K0/Kx2 and 78K0S/Kx1+?

Answer:

The 78K0/Kx2 and 78K0S/Kx1+ are both 8-bit All Flash microcontrollers, but they employ different microcontroller cores. For the differences in core, refer to A3 of "Differences among 8-bit microcontroller products (78K0/78K0S)".
In addition to pin count (and thus port count) and core differences, there are also the following functional differences.

78K0/Kx2

78K0S/Kx1+

Operating power supply voltage

1.8 to 5.5 V

2.2Note 1 to 5.5 V

Maximum operating frequency

20 MHz

10 MHz

ROM size

8 to 128 KB (Banks are used for 64 KB and above)

1 to 8 KB

RAM size

512 bytes to 7 KB (high-speed RAM: Up to 1 KB)

128 to 256 bytes (high-speed RAM only)

16-bit timer

1 or 2 channels

0 or 1 channel

8-bit timerNote 2

4 channels

1 or 2 channels

- Carrier generation

1 channel

None

Watch timer

Provided in some products

None

Buzzer output, clock output

Provided in some products

None

Watchdog timer

1 channel

1 channel

- Window function

Provided (4 stages)

None

- Illegal memory access detection

Provided

None

- Count clock

Fixed to low-speed internal oscillation clock

Low-speed internal oscillation clock or system clock

A/D converter (10 bits)

8 channels

None or 4 channels

Serial functions

- UART

2 channels

0 or 1 channel

- CSI

1 or 2 channels

None

- CSI with automatic transmit/receive function

Provided in some products

None

- I2C bus

1 channel

None

Key return interrupt

Provided in some products

None

Multiply-divide circuit

Provided in some products (16x16, 32/16)

Provided in some products (8x8)

POC

1.59 V or 2.7 V

Fixed to 2.1 V

Internal regulator

Provided

None

LVI

Power supply voltage/external pin

Power supply voltage only

Reset pin function

Reset pin

Reset/input port

System clock

Startup with high-speed internal oscillation clock, then selectable by program

Specified in option byte

Peripheral clock

System clock/high-speed internal oscillation clock

Selectable as a division of system clock

Flash memory

- Memory size specification function

Provided

None

- Programming with writer

UART/CSI

Use of X1 and X2

- Block size

1 KB

256 bytes

- Boot swap

Provided

None

- Mode control switching

Dedicated FLMD0 pin

Shared with X1

- Security function

Erase and rewrite are prohibited through specification with a security command or by the programming writer.

Erase and rewrite are prohibited with the protect byte.

- Self programming

Startup with FLMD0 pin

Startup with special sequence

Peripheral access arbitration

Arbitration with waits

None

Note 1: Including POC voltage variation (2.0 to 2.2 V)

Note 2: The supported timer functions differ.

Remark: This table lists only the main differences. For example, the source clocks that can be selected with the timer differ, the default state of the pins shared with analog input differ (analog input for the 78K0/Kx2, digital input for the 78K0S/Kx1+), and the various settings not listed in this table also differ.
Moreover, there are also differences in characteristics: the accuracy of the high-speed internal oscillation clock is ±5% for the 78K0/Kx2 and ±5% (±3% when the temperature is restricted) for the 78K0S/Kx1+.